The present invention relates to a portable terminal device suitable for use as a cellular phone, a PHS (Personal Handyphone System) phone, a PDA (Personal Digital Assistant) unit, an electronic dictionary unit, a portable navigation unit, or the like.
At present, there is known a slide-type cellular phone having a casing assembly made up of a lower casing and an upper casing that is slidable against the lower casing to open and close the casing assembly. When the upper casing is fully slid against the lower casing to open the casing assembly, slide grooves of a slide mechanism are revealed on the reverse side of the upper casing. The revealed slide grooves make the cellular phone look poor in appearance. In addition, since the slide grooves are in the form of holes, when the upper casing is fully slid against the lower casing to open the casing assembly, dust and dirt particles tend to enter through the slide grooves into the casing assembly.
Japanese Patent Laid-Open No. 2003-319042 discloses a portable terminal device that is designed to eliminate the above drawbacks. As shown in FIG. 15 of the accompanying drawings, the portable terminal device includes a front casing 201 having a pair of teeth 203 of a substantially T-shaped cross section and a rear casing 202 having a pair of guide grooves 204 that are as long as the area in which the front casing 201 and the rear casing 202 face each other.
The teeth 203 on the front casing 201 slidably engage in the respective guide grooves 204 in the rear casing 202. The guide grooves 204 allowing the teeth 203 to slide therealong from ends 204a thereof to other ends 204b thereof.
Since the length of the guide grooves 204 is limited within the area in which the front casing 201 and the rear casing 202 face each other, even when the front casing 201 is fully slid against the rear casing 202 to open the casing assembly, the guide grooves 204 are not exposed out of the area in which the front casing 201 and the rear casing 202 face each other. Therefore, when the casing assembly is opened, the guide grooves 204 are not exposed, so that the portable terminal device does not look poor in appearance and dust and dirt particles do not enter through the guide grooves 204 into the casing assembly.
In the portable terminal device disclosed in Japanese Patent Laid-Open No. 2003-319042, the front casing 201 and the rear casing 202 are operatively connected to each other by the two teeth 203 and the two guide grooves 204. Stated otherwise, the front casing 201 and the rear casing 202 are operatively connected to each other at two positions by the teeth 203 engaging in the guide grooves 204. Accordingly, the strength by which the front casing 201 and the rear casing 202 are connected to each other is relatively weak.
Furthermore, inasmuch as the front casing 201 and the rear casing 202 are supported by the teeth 203 and the guide grooves 204, they tend to wobble vertically when they slide against each other, and may not slide smoothly against each other.